transmitted past the segments while decreasing diffraction effects. Simple 

 diffraction diagrams (i.e., Figures 2-42 to 2-52 of the SPM) can be used to 

 compute the diffraction effect on a wave which passes through a gap. However, 

 these simple diffraction diagrams do not account for wave shoaling or break- 

 ing. If the design wave breaks before passing the breakwater, isolines which 

 predict the diffraction coefficient will predict values that are higher than 

 should actually be expected. The effects of wavelength and the ratio of gap 

 size to wavelength on the diffraction pattern are clearly demonstrated by 

 comparing the wave patterns in aerial photographs taken at two different times 

 at Lakeview Park (Figure 11). The shorter incident waves in Figure 11a are 

 less distorted after passing through the gaps, and the shadow zones are rela- 

 tively quieter than for the longer incident waves shown in Figure lib. The 

 shoreline tends to align itself with the waves; therefore, the salients are 

 more pronounced with longer, more diffracted waves. 

 Wave angle 



31. The orientation of the incident waves relative to shore and the 

 breakwater affects both the degree of salient development and the equilibrium 

 planform of the shoreline. Strongly oblique waves will drive a regional long- 

 shore current that may dominate the local effects of the breakwater, restrict- 

 ing the size of the salients and preventing connection to the structure. 

 Accordingly, it is important when designing a breakwater to consider not only 

 the predominant wave direction, but also the average annual wave angle distri- 

 bution. Two regions might experience identical levels of wave energy, but if 

 one region has a more diverse wave angle climate, this site may require a 

 longer breakwater to suppress the effects of the more oblique waves. A ter- 

 minal structure may also be required to reduce alongshore losses. The bimodal 

 distribution in wave direction common to many coasts may be a particularly 

 important consideration in breakwater design. A postulated criterion for 

 salient development based on this factor is presented in Walker, Clark, and 

 Pope (1981) and is reviewed in Appendix A. Shoreline planform is highly 

 dependent on the directional characteristics of the wave climate. The bulge 

 in the shoreline tends to align itself with the predominant wave direction. 

 This is particularly noticeable for tombolos, which seem to point into the 

 waves (Figure 4). Frequently, the feature's updrift side is filled, its apex 

 is near the center of the structure, and the downdrift side is less filled or 

 even eroded. However, if predominant waves are extremely oblique to the 



31 



